Hi all,
I'm having a weird state problem with
Component<https://github.com/stuartsierra/component>.
Let's say I have a system component, like in fig.1. Starting / stopping and
loading state is fine.
However, let's say I have 2 other components (:updater , :reader) that use
component :a. This is the problem that occurs.
1. When *:updater*, modifies an atom in *:a*, that change appears in
path [*:core :a*], not path [*:updater :a*] or [*:a*].
2. Because of the abouve, when *:reader* goes to it's local path [
*:reader :a*] to read that change, it doesn't see those modifications.
3. Using this scheme, *:a* is duplicated 4 times, in the system map.
However, the modifications only appear in path [*:core :a*]. Thus
:reader is unable to access it (it's local [*:a*] is unchanged).
(def system-components [:a :updater :reader])
(defrecord Core [env] component/Lifecycle
(start [this] ...)
(stop [this] ...))
(defn component-core [env]
(component/system-map
:a (component/using
(ca/component-a env)
{})
:updater (component/using
(cs/component-updater env)
{:a :a})
:reader(component/using
(cs/component-reader env)
{:a :a})
:core (component/using
(map->Foobar {:env env})
{:a :a
:updater :updater
:reader :reader })))
*fig.1 *
I was hoping to use Component to manage all internal application state. But
maybe it's not designed for this use case (state changes between
components). I imagine that immutability is preventing all those duplicates
from seeing the modifications. However, in this case I do need an update to
:a in one component, to be accessed by another component.
Any suggestions on patterns here? I'm also looking at
component/update-system<https://github.com/stuartsierra/component/blob/master/src/com/stuartsierra/component.clj#L116>.
But again, I don't have access to the core *system* var, from within my
components.
Any insights appreciated
Tim Washington
Interruptsoftware.com <http://interruptsoftware.com>
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